Disproving the proposition can often be impossible, given the parameters. How many angels are their on the head of a pin? How long is a day 12 light years hence? How many life times does the average human repeat? These matters cannot be settled, in human terms, and thus cannot be proved or disproved. Such is the situation where matters on the alien presence cross the human desire for control. This is a multifaceted confusion. There are aliens in the Service-to-Self orientation that can wield deception better than the most practiced human. There are humans in establishment positions who will cloud the issue endlessly, as long as they can stay in control. There are humans who desire to profit from the alien issue, and cook up scenarios and roles for themselves as long as there is an audience. Where does the truth lie, and how can the truth be proven?
Unfortunately, this is not a matter that can be quickly put to rest. The issues at play are many, and involve the free will of man, the engagement rules that govern alien interaction with man, the engagement rules that govern alien interaction between orientations, and the mutability of truth itself. Different people see truth in different ways.
In all of this rises the issue of whether a given alien message, such as ours, is truly from ourselves or Nancy's imagination or government psychics. How can this matter be proved? It cannot. Psychics can insert themselves into others thoughts. Imaginative humans can and do concoct intriguing stories. And the truth can be before you, unrecognized and even rejected. It is for you to judge, listening with your heart and pondering with your mind. And when you have determined what is true, for you, then this you should hold to. It is, at essence, a matter of faith.